Certain polymeric materials such as poly(vinyl chloride) (PVC) and cellulose esters such as cellulose acetate, cellulose acetate propionate and cellulose acetate butyrate must be plasticized to be processed into molded or extruded objects. Most other thermoplastic resins such as polyesters, polyamides and polyolefins do not typically contain a plasticizer when processed in the molten state to form rigid molded or extruded objects. However, the use of plasticizers in polyester compositions has been disclosed for various applications.
U.S. Pat. No. 4,450,250 to McConnell et al. describes adhesive compositions based on amorphous or crystallizable polyesters having a melting point in the range of 80 to 230° C. containing 1 to 35 weight percent of selected plasticizers.
U.S. Pat. No. 4,340,526 to Petke et al. describes hot melt adhesive compositions based on certain terephthalate and 1,4-cyclohexanedicarboxylate polyesters containing 10 to 35 weight percent of benzoate or phthalate plasticizers. The plasticizers are present to lower the melt viscosity of the polyesters in order to facilitate their use as hot melt adhesives.
Japan Patent No. 02 986197 to Kiyomi et al. describes extruded flat or tubular film based on polyesters plasticized with 1 to 40 parts of several types of plasticizer per 100 parts of polyester, i.e. up to 28 weight percent plasticizer in overall composition. Many of the plasticizers cited are of an aliphatic nature. The films are used as shrink films.
U.S. Pat. No. 5,624,987 to Brink et al. describes polyester compositions comprising a blend of poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) copolyesters containing at least 80 mole percent of 1,4-cyclohexanedimethanol (CHDM) and 0.5 to 25 weight percent of one or more polyalkylene ethers. These ethers decrease the glass transition temperature (Tg) of the polyester, increase the rate of crystallization and allow the use of low molding temperatures.
U.S. Pat. No. 5,824,398 to Shih describes heat shrinkable film or sheet comprising 90 to 99 weight percent of a polyester having a Tg in the range of 40 to 150° C. and comprising at least 80 mole percent of aromatic dicarboxylic acids having 8 to 14 carbon atoms and at least 10 mole percent CHDM and 1 to 10 weight percent of a monoglyceride having 5 to 35 carbon atoms. The monoglyceride lowers the Tg of the blend.
U.S. Pat. No. 4,391,938 to Memon describes polyethylene terephthalate (PET) compositions containing 1 to 10 weight percent of an additive to improve the crystallization rate of the polyester and to improve the surface appearance of molded parts. Additives include certain plasticizers, fast crystallizing polyesters such as poly(butylene terephthalate) (PBT), glass fibers and talc, which would act as a nucleation agent in PET.
Anonymous Research Disclosure 23314, September 1983, describes polyester compositions having improved gas barrier properties for use in making film or sheet. The polyesters contain 80 to 99 weight percent of a homo or copolyester containing an aromatic dicarboxylic acid such as terephthalic acid and one or more glycols containing 2 to 12 carbon atoms and 1 to 20 weight percent of benzoic acid esters or phthalic acid esters.
Great Britain Patent No. 815,991 to Goodale et al. describes a process for making dibenzoate esters from glycols and butyl benzoate using a calcium oxide ester exchange catalyst. These esters are reported to be plasticizers for PVC resins.
U.S. Pat. No. 3,186,961 to Sears describes polycarbonate resins plasticized with a wide range of plasticizers. The molten blends must be quenched to achieve the desired properties. The presence of the plasticizer increases the rate of crystallization of the polycarbonate.
U.S. Pat. No. 2,044,612 to Jaeger describes plasticizers for several polymeric materials such as cellulose esters, phenol/formaldehyde resins, urea resins and the like.
Great Britain 1,323,478 (1973) assigned to Stamicarbon N.V. describes the preparation of dibenzoate plasticizers for use in PVC and poly(vinyl acetate) compositions
In the manufacture of film and sheet, processes such as calendering and extrusion are used to produce film and sheet from a wide variety of plastics. Calendering in particular is used to produce film and sheet from plastics such as plasticized and rigid PVC compositions. On a smaller scale, other thermoplastic polymers such as thermoplastic rubbers, certain polyurethanes, talc-filled polypropylene, acrylonitrile/butadiene/styrene terpolymers (ABS resins) and chlorinated polyethylene are sometimes processed by calendering methods. U.S. Pat. No. 6,068,910 to Flynn et al. discloses the feasibility of calendering certain polyesters having a crystallization half time from the molten state of at least 5 minutes to provide film and sheet. Although this patent recognized the need for processing aids to prevent molten polymer from sticking to the calender rolls, large concentrations of plasticizers were not used.